Process for bonding cement and gypsum



Patented Aug. 39, 1932 stares CLOYD 1VL- GHAPMAN,- F DOUGLASTOZN; NEW YORK r noonss Fort BONDING CEMENT Ann GYPSUM No Drawing. I

My invention relates to the applicationof coatings composed in whole or in part of cement to surfaces of structural units or portions of structures composedin whole or in p part-of'gyp'sum, and to the-application of coatings containing gypsum to} surfaces of structural units or portions of structures containing cement and has for its object the providing or" an adequate bond between the two materials.

Great difficulty' has been experienced 1n the past in applying acoating of mortar in Which cement constitutesthe active cementing material to a structure builtjof gypsum or a material in which gypsum or plaster of Paris constitutes the active cementing'material.

It is a common practice in present day 7 building construction, to form partitions, v

walls, floors, roofs and ceilings of gypsum or of mixtures of materials: in Which gypsum k is the' active constituent which causes the mixture tosetand harden after the product is formed. In many cases partitions, floors or other portions of a structure are composed of structural units of material composed Wholly orpartially ofcalcined gypsum, commonly call-ed gypsum or stucco, Which g have beenmanufactured in afactoryand are the site of the structure and poured into forms and allowed to' harden in place in the floor or root of the building. Such con- I struction is commonly known as poured-inplace construction to distinguish it from the pecast unit construction described above.

is frequently desired to apply to one or more ot the surfaces a coating of mortar or plasterjcomposed wholly or in part of Portland commonly known as precast units. In

other cases, particularly in floors and roofs,

' the 7 sum mixture ismixed with water at sum In both of these classes of construction it Application filed. January. 28, 1928., Serial No 250,341.

1 time the'c'ement' mortar or plaster scales oii' ,or comes loose.

There are many conditions under which it is highly desirable to apply cement or ce-h mentmortar directly to" gypsum. Ifce'ment mortar could be depended upon to adhere firmly and permanently to gypsum it would be possible to construct the outside walls of buildings of gypsum'and then cover the out A,

side surface of the gypsum wall with a; coat- '80 ing' of cement stucco to protect it from the disintegrating and damaging effects of weather exposure; V c

.Gyp'suin absorbs water yerygreedily and, is not, of itself, considered a suitable material for the'construction of outside walls exposed to theact'ion: of. the weather, but such walls, properly protected from the elements by afirmly adheringfcoat of cement mortar-, would successfully Withstand the effects of even sey'erefclimatic conditions.

Another example of conditions under which it is desirable to be able to" firmly'bond cement mixtures to gypsum'is in the case of a gypsum 'floor over whicha wearing course" orlayer ot'some sortisl to be placed. When the rough floor is finished and ready for the reception of the Wearing. co'urse, it must be brought to a smooth, even, level surface by the application of some sort of surfacing ma-BO teri-al; If a cement mortar could-be applied in a manner :Which would insure its having a stron firm bond with the underlying gypdoor, there would result a finished sur-. face which would be hard, smooth, wear resisting and suitable for the reception of linoleum, cork, carpet; rug,'or otherform of vfloor covering.

When the structuralunit is composed of "cement concrete or cementmortar or when the portion of the structure" is composed of concrete or cement mortar and it is desired to apply thereto a,plaster or mortar'in which gypsum is the cementing'constituent, it is just as essential'that there" be a firm, tenacious bond between the two materials. Structures,

walls, partitions, roofs, etc. are frequently built of "concrete building blocks, brick or slabs, or the structure may be of concrete poured place, and it is frequently desired plied to concrete, I can produce abond be tween the two materials which is so strong and tenaclous that,when broken apart by force or shock, they will not separate at the which is a chemical method involving the.

gypsumby .incorporating in it, whilethel.

bond but will break apart either in the gypsum portion or in the cement portion depend- V upon which is theweaker of the two.

methods of securing this bond. the first o treatment of the surface of thegypsum, with a chemical solution, and the other of which involves the preparation of the surface of the gypsum is'still plastic before itlias set, a

powdery or granular material which will bond strongly with the gypsum and to which 4 in turn cement will firmly adhere.

I find that there is a third method of producing this. bond which consists in mixing gypsum, I .QQt a firm, stron betweenthe gypsum and the cement mix .50

with the cement or the cement mortar or mixture containing cement or with the gypsum or mixture containing gypsum, a chemical which has the desired bonding effect. I find that the chlorides which when applied to the surfaceof a material containing gypsum will cause it to bond firmly with cement or mixtures containing cement, may be added to the cement, or tothe mixture containing cement. I find that when I adda chloride, as for example, calcium chloride, to cement or to a mixture containing cement, such for example Crete, and-apply. the mixture to the surface of g, tenacious bond ture after the latterhas set andhardenod.

1 The same is true when the chloride is added V In practice I usuallydissolve the chloride to .afgypsum material which is to be applied to a surface containing cement.

- gauging the-cement or mixture containing cement before applying itto thesurface of the gypsum. But I find that it is not necesstances containing'.chloride, asfor example, 2

sary to apply the chemical in the form of a solution." I find thatsomechlorides or'sub- C211,; (which is a patented compound, containing hydrated lime and chloride of lime) maybe mixed with thedry cement and there- A after this dry mixture of cement and chloride a chloride. Other chlorides have V In my co-pending applications, Serial Nos. 242.301and 246,906, I haye described two may be mixed with sand or other aggregate ing mortar or concrete be applied to the surface of gypsum and that a satisfactory bond is thereby secured. I follow thesame procedure in preparing a material containing gypsum for application to a surface containing cement.

I find that a number of chemicalscanbe used to impart to the applied cement or gypsumthe' desired bonding quality. Chlorides are particularly suitable but to somewhat varying degree. Some chlorides have a detrimental efiect upon the quality of cement, its hardness and strength after setting. Such chlorides should not be used for the purpose of securing a bond to gypsum. Sodium chloride, common salt, is an example of such a hardening and accelerating effect upon cement and its setting qualities and hasten the timeof set to a marked degree. Calcium chloride is an exampleof suchachloride. I prefer calcium chloride for this reason and also on account of its cheapness and general availability. As to the strength of the solutions used in gauging cement or gypsum mixturesto produce a suitable bond, or the amount of chlorides added to cement to produce a mixture which when wet will produce a suitable bond, I

water to be a'very satisfactory strength.

- When the bonding agent is mixed in the dry form with the cement or gypsum, I find p I I I p I N that the use of equlvalent amounts to give as a cement-and-sand mortar or a cement con- 1. The process of producing a bondlbetween a material containing hydraulic gyp-= sum and a material'containing cement, one of which materials is applied in a' plastic state to the other after it has set and hardened, which consists in mixing between one quarter per cent. and ten per cent. of achloride with the material which is applied in a plastic state before applying it.

2. The. process of producing a bond.'between a material containing gypsum and a material containing hydraulic cement, one of whichmaterials is applied in .a plastic state to the other after it has set and hardened,

so l

which consists in mixing between one quarter per cent. and ten per cent. of calcium chloride with the material which is applied in a plastic state before applying it.

3. The process of producing a bond between a material composed largely of gypsum and a material composed largely of cement, one of which materials is applied in a plastic state to the other after it has set and hardened, which consists in mixing between one quarter per cent. and ten per cent. of a chloride with thematerial which is applied in a plastic state before applying it.

4. The process of producing a bond between a material composed largely of gypsum and a material composed largely of cement, one of which materials is applied in a plastic state to the other after it has set and hardened, which consists in mixing between one quarter per cent. and ten per cent.'o-f calcium chloride with the material which is applied in a plastic state before applying it.

5. The process of producing a bond between a material containing gypsum and a material containing cement one of which ma terials is applied in a plastic state to the other after it has set and hardened, which consists in mixing a. material containing from one quarter per cent. to fifty per cent. of a an chloride with the material which is applied in a plastic state before applying it.

6. That step in the process of bonding cement to gypsum which consists in adding a soluble chloride to the cement before apply in the cement to the gypsum.

That step in the process of bonding ce I ment to gypsum which consists in adding chloride of calcium to the cement before applying the cement to the gypsum.

4o 8. That step in the process of bonding a mixture containing Portland cement to a mixture containing gypsum which consists in adding to the mixture containing cement,

- a solution of chloride before applying the cement to the gypsum.

9. That step in the process of bonding a mixture containing Portland cement to a mixture containing gypsum which consists in adding to the mixture containing cement a solution of a chloride in the proportion of from one-half pound to five pounds of chloride for each gallon of water used before applying the cement to the gypsum.

Signed at New York city, in the county of New York and State of New York this 27th day of January, A. D- 1928.

CLOYD M. CHAPMAN. 

